Method and apparatus for burning pulverized fuel



Den. 30, 1930. v v J. E. BELL; Y 1,785,837

METHOD AND APPARATUS FR BURNING PULVERIZED-FUEL ml'ed April 13, 1922 3sheets-sheet 1.

I VEN TOR J. E. BELL. 1,786,887

METHODVANDAPPARATUS FOR BURNING PULVERIZED FUEL Dec. 30,1930.

Filed April 15, 1922 3. sheds-sheet 2 1N VENTOR TToRNE YS //f//f Hummm@I? Y '2%- y mmnmmn gb Y Mmmm@ l METHOD AND APPARATUS FOR URNINGPULVERIZED FUEL Filed April 15, 1922 3 Sheetlssheet A3 ,/f I y "QWITNESS AATTORNE Y Patented* Dec. 30, 1930 UNITED STATES PATENT ori-ICE.JOHN E. BELL, OF

BROOKLYN, NEW YORK, ASSIGNOR TO, COMBUSTION ENGINEERING CORPORATION, ACORPORATION OF YORK METHOD AND APPARATUS FOR `BURN ING PULVERIZED FUELApplication led April 13,

o This invention relates to a method of and apparatus for burningpulverized fueland vit is especially useful in stationary boilers forthe generation of'steam. f

One of the primary objects of my invention is ,to secure more efficientandmore perfect combustion. Y Another object is to more effectivelyutilize the space of the combustion chamber for combustion purposes.

More specifically stated, my invention contemplates the admission of thefuel in such manner that ignition of some'of the fuel takes place veryquickly after introduction, thereby holding the iiame near the burnermecha# nism. It also` contemplates ignition taking place over anextended area whereby a maximum portion of the space ofthe combustionchamber is filled with fiame and utilized for combustion purposes; andwhereby, among other things, the process vof complete combustion isexpedited,vor, stated in another way, whereby a given amount ofpulveriz'ed fuel can be burned ina combustion chamber of smaller size.`x

'25 The foregoing, together withosuch other objects or advantages as mayhereinafter appear or are incident to my invention, I obtain by means ofa process and apparatus illustrated in preferred form in theaccomao'panying drawings, wherein:

Fig. 1 is a section through a combustion chamber .of a Water tube boilerof the hori-y zontal type and illustrates one form of my invention; Fig.2 is a similar section show'- ing another form of my invention; Fig. 31s an enlarged end elevation of one form of burner mechanism which maybe utilized in lcarrying out my invention; Fig. 4 is an elevation of theburner of Fig. `3; Fig. 5 1s a section through the burner taken on theline 5-5 of Fig. 4; Fig. 6 is a section through the burner taken on theline 6-6 of Fig. 5; Fig.

" 7 is a bottom plan view of the burner of Fig.

6; Fig. 8 is a fragmentary section of another form of burner; and Fig. 9is a bottom/ plan of the burner of Fig. 8. Y

Heretofore, in the artof burning pulverl ized fuel iii-.stationaryboilers, it has been V customary to admitthe fuel either by means 50 ofvroundlburners or at burners-sometimes 1922. Serial N0, 552,258.

calledfish-tail burners-and ignition of the fuel, assumino that thefurnace has been in operation and is hot, takes place at a well definedpoint, the distance between the burner and the point ofignitiondepending upon the velocity at which the fuel, or a mixture of the fueland air, was admitted. By this arrangement, among other things, it wasnot possible to hold the flames very closely to the burner, and thus itwas not possible to utilize a maximuml portion of the available space ofthe combustion chamber for combustion purposes.

In accordance with my invention, I propose, inter alia, to admit fuel todifferent portions of the combustion chamber, at relatively dierentvelocities, so that eddying and ignition will take place at relativelyearlier or later stages, making it possible to more eifectively utilizethe available space fon combustion and to spread or diffuse the amesmore nearly throughout the combustion. chamber, and to hold them upvtoward the burner. ing the desired result may be employedbut in thepresent instance I have shown a single' burner mechanism, constructedyso as t0A de# liver the fuel in the manner herein described.

Referring now to Figs. 1 and 2, the combustion chamber A is roughlyrectangular in vertical and horizontal sections; has an outlet 7 in theupper part thereof for the hot products of combustiomthe evaporatingIsurfaces, in this instance water tubes 8,-extending over such outlet;'and is provided with a battery of auxiliary air inlets 9 extendingthrough the front Wall 10 and arranged in horizontal rows, the number ofinlets and rows of inlets being dependent upon the size of theparticular furnace. These air inlets are damper controlled. In thetbottom of the combustion chamber there is a door 11 for the removal ofash. In the embodiment shown the fuel is preferably delivered into theupper portion of the combustion chamber in a ldownward direction byburners B, the number of which depends upon the horizontal length of thecombustion chamber. These burners are adapted to deliver either `thepulverized coal'or a mixture of Various ways of accomplishpulverizedcoal and air-preferably the latter-and their construction will nowy bedescribed.

Each burner comprises a casing 1Q., open at the bottom and provided withan air inlet 13v on one side near the top. This casing is divided intotwo compartments 14 and 15 (see Fig. 5) by a division Wall or septum 16,such wall preferably terminating a short distance above the bottom ofthe casing. The passage 14 is controlled by a damper 17 operated `by thegearing 18, shown in Fig. 3. The burner nozzle 19depends from the upperends of the casing and extends down into the compartment 15, 'the lowerend of the nozzle terminating a short distance (above the lower end ofthe division wall 16. The nozzle changes from a round section at the topto an elongated narrow section at the bottom, thus being somewhatsimilar to the fish-tail type. The flow of air induced by thedraft-which is preferably created by a stack, not shown-'through theinlet 13 and down through the passage 15, on either side of the nozzle19, is controlled by means of dampers 2O and 21, out so as to surroundthe nozzle when closed, as indicated in Fig.l 5. The dampers areoperated by gearing 18, as before. A mixture of fuel and air is suppliedto the nozzles by means of pipes 22, leading to a suitable source ofsupply, the amount of velocity of the air being preferably in theneighborhood of that required for carrying purposes from the feeders tothe burners. The burner mechanism in all of the forms of myinventionldisclosed is the same, with the exception of the mouth of thenozzle.

These nozzles have been made with the area substantially constantthroughout, that is to say, the change in cross section from a circle atthe topto a long slot at the bott-om, has been graduated so as to securea substantially constant area throughout. In a nozzle of this character,the fuel or mixture of fuel,

and air will pass therethrough in a substantially stream line, and as aconsequence, since the friction is less, the eddying at the surfaces ofthe column of fuel delivered is not pronounced, so that the coal doesnot ignite so readily and neither does the column expand materially incross section before substantial gasification takes place.

By experimentation I have found that by properly flaring the mouth ofthe nozzle, with anozzle duct of sufcient length, that a column of fuelwill be delivered having the following characteristics: The centralportion of such a column will retain its relatively high velocity andits stream line flow characteristic for a longerperiod of time and will,therefore, penetrate more deeply into the combustion chamber beforeignition takes place and eddying is set up; While the outer portions ofthe column will diverge somewhat sharply from the central portionand'wll travel at a portions of relatively lower velocity, with theresult that in such portions of the column the stream line flowcharacteristic is lost much sooner, eddying is quickly set up, andignition takes place more promptly. As a result, ignition, instead oftaking place at a localized point, takes place over an extended area andthe flame is held well up toward the burners and is diffused throughouta greater proportion of the combustion chamber. IThis, in addition toreducing the length of travel from the burners necessary to completecombustion, also secures more rapid and more perfect combustion byreason of the fact that there is a greater diffusion and also a greatersurface exposure of the fuel particles `and the gases liberated, making'it more certain that the particles of coaland gases are surrounded andmixed in with oxygen bearing air, 1n-

duced through the burners und through the' inlets 9. The induced airtravels at a lower velocity than the incoming fuel, so thatv theparticles of the latter are, `in afsense, projected through slowermoving bodies of air with the result that as combustion is initiated inthe particles, the latter are scoured andthe gases emanating therefromare removed from the surfaces of the coal particles in the process,thereby ensuring exposure of not only the coal but the gas molecules tofresh air. In this -latter connection, 'attention is directed to thefact that the incoming stream of fuel is surrounded by air inducedthrough `the passage 15, and additional air is supplied through thepassage 14 to the space between the descending and the nascendingsupplied through the inlets 9 carries the additional oxygen ne ded forcompletion of combustion.

The air induced through the inlets 9, par ticularly the lower inlets,follows, to some extent, the general stream line fiow of the fuel andflame stream providing a bordering stream of air into which the heavierunconsumed or partially consumed particles of fuel may gravitate andthere find the oxygen needed for the completion of combustion. At thesame time a body of cool air is ensured in the bottom of the combustionchamber, of sufficient depth to cool the precipitating -ash belowsubstantial slag forming temperature lation of the dampers 17, 20 and'21themo-l mentum of the streams of air drawn through the passages 14 and15 can be regulated so as not only to provide proper amountsl of 'airimmediately around the incoming lfuel, but also to prevent unconsumedfuel and-gases the flame stream, while the air Maase? being drawnimmediately around the inner end of thel top wall 23 into theevaporating surfaces. By proper manipulation of the dampers, themomentum of the air passing3 A tions on the inside are more pronouncedthan they vare onV the outside of the nozzle. These serrated forms arepreferred for the following reasons: T he stream, where it issues fromthe straight portions of the nozzle mouth, retains substantially all ofits high velocity and has very little diverging tendency and deliversthe fuel to ,the lowest part of the furnace. The center of the streamissuing from the flaring parts of the nozzle mouth retains some of itshigh velocity and carries the fuel down into the combustion chamber butnot as far as the stream issuing from the intermediate straight parts,and there is a more marked tendency to diverge. rlhe outer portions ofthe stream issuing from the flaring portions, travel at stilllowervelocity and diverge rather. sharply. Thus, diierent portions of thecolumn of fuel, considered as a whole, travel at 'dierent relativevelocities, retain their stream line Sow characteristics relatively moreor relatively less and eddy more or less freely, as the case may be. Inconsequence, as point-ed out, ignition is more widely spread, the amesmore widely diftional area of the delivery orice of the pipe beinggreater than the cross-sectional area of the pipe at the region Wherethe flaring begins.

2. The method of 'delivering a mixture of pulverized fuel and air to acombustion chamber which consists in causing the mixture to move in astream circular in cross section, in gradually changing the stream incross-section from circular to a thin. wide sheet of approximately thesamearea in cross-section, and then in causing the' sheet to 'expand ata multiplicity of spaced points along its Wide dimension and deliveringit int/o the chamber.

ln testimony whereof, I have hereunto signed my name.

JOHN E. BELL.

fused and combustion more rapid and perfect.

ln a sense, therefore, the serrated nozzle has the eiectof a groupofsmallnozzles having alternately straight and flaring discharge ends;and in addition to the advantages previously noted, the process ofcombustion is hastened, because the central portion of the fuel streamis projected a substantial distance through a slower moving body ofiame, to the heat of which it is subjected.

l claim: 1

l. powdered fuel burner comprising a nozzle pipe having a fuel inlet endand a fuel delivery end, said pipe being approximately circular-.incross section at its inlet end and being gradually attened and widenedout from the ,inlet end to the fuel delivery end to provide a wide thindelivery slot .at said deliver end, the wall of-the pipe at the tip of te delivery end being flared outwardly at a multiplicity of spacedpointsv along the longfdimension of the delivery end, so that thedelivery orice in face view presents a plurality of s aced narrow'portiils with Y intermediate ared, portions9 the ciloss-see vse

